A portable microfluidic <i>in vitro</i> diagnostic device for rapid detection of procalcitonin

Rapid and sensitive detection of targeted biomarkers in trace samples is of great significance for early in vitro diagnosis of diseases. Microfluidic technology has competitive advantages in this field due to its low cost, high efficiency, and high portability; however, the analysis of results tends to rely on bulky and sophisticated instruments, and this limits its applications. In this work, we developed a Raspberry Pi camera-based biomarker detection device based on microfluidic technology and digital image colorimetry. For highly sensitive biomarker detection on microfluidic chips, we propose a three-step signal-amplification colorimetric detection strategy consisting of: (1) the release of Ag+ ions from silver nanoparticles, (2) Ag+-inhibited urea hydrolysis colorimetry, and (3) microscopic lens magnification. For efficient evaluation of results, we employed an RGB image-processing system to quantitatively analyze color images captured by the Raspberry Pi camera. Further, we tested the functionality of the device with procalcitonin (PCT) in phosphate-buffered saline, plasma, and serum to simulate clinical situations. We determined the limit of detection as 1 ng/ml, and a good linear relationship was established between PCT concentration and color intensity within the detection range 1–10 ng/ml. Importantly, only a relatively short detection time (40 min) was required in all three environments. The results demonstrate the great potential of this device for biomarker detection and facilitating biomedical research.